Add vec::IntoIter and fold test.
Add vec::IntoIter and fold test.

graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust,rust-lang/miri,aidancully/rust,aidancully/rust,GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust,GBGamer/rust,GBGamer/rust,tsion/miri,graydon/rust,GBGamer/rust,aidancully/rust,aidancully/rust,rust-lang/miri,rust-lang/miri,rust-lang/miri